BAMAKO, Mali -- An image evoked by mentioning the leaders who rule Africa is often this: A young military officer, after shooting his way to power, promotes himself to general. He bans political parties except the one he controls.

Color portraits of the president hang in every store and restaurant. He insists on being called "doctor" or the "guide" or the "No. 1 peasant." He is the richest man in the land. He does not run for election, ever.

For nearly three decades, all but a handful of African nations have been run to some degree as single-party states under a powerful authoritarian leader. The only way that governments changed hands was by military coup, or in the relatively rare instances when a ruler died in office of natural causes.

But in just a few months, pro-democracy challenges to Africa's entrenched autocratic leaders have grown to the point that many are in greater danger of being deposed than ever. And their demise is likely to forever alter the highly personal style of rule that has dominated the continent since the first wave of decolonization 30 years ago.

Last month, Benin's president, Brig. Gen. Mathieu Kerekou, after 18 years of military rule, became the first African leader on the mainland to be voted out of office.

In February, new governments took over in two small island nations off the West African coast, Cape Verde and Sao Tome and Principe, after multiparty elections.

Elsewhere, vigorous political campaigns are under way challenging long-tenured rulers in at least a dozen countries run by single-party or military leaders, including Congo, Ghana, Togo, Guinea, Kenya, Zambia and Zaire.

Taking note of these developments, Abass Bundu, executive director of the 16-member Economic Community of West African States, said Africa was in the middle of a "hurricane of change which is now irreversible." Those leaders choosing to resist this trend, he said in a recent speech, were inviting "peril or oblivion."

Despite such declarations, it is unclear whether the challengers or the challenged are more vulnerable to the dangers implicit in the power struggles flickering across the continent.

In Benin, a process that began last year with protesters tearing down statues of Lenin and Marx first forced General Kerekou to accept a caretaker government led by Nicephore Soglo, a former World Bank official who was prime minister and defense minister. When he then ran against Mr. Soglo in a free election, General Kerekou lost by a 2-1 margin.

More recently, hundreds have died as demonstrations convened to demand greater and more open political choices have been suppressed, from Zaire, in the south of the equatorial coastal region, through Gabon, Cameroon and Togo, and last month in Bamako, where diplomats estimate at least 200 people died in five days of protests that ultimately led to the overthrow of Gen. Moussa Traore.

Quite often the political tumult is accounted for with the same simple explanation: the drastically impoverished life of most Africans. Economically, much of the continent is not standing still but moving backward.

"For many people, things are so bad that they have nothing to lose," said Demba Diallo, a human rights activist in Mali and one of the leaders of the pro-democracy movement that forced General Traore from the power he had accumulated for 24 years.

What some officials see as a more immediate catalyst for change than the long-standing processes of pauperization have been the collapse of communism in Eastern Europe and the demise of apartheid in South Africa, which demonstrated how seemingly powerful regimes and systems could be swept away.

"Africans aren't stupid," said Laurent Gbagbo, a history professor and political activist in the Ivory Coast. "They see what zTC is happening elsewhere, and they are determined to fight for their rights here, too."

Underlying the trend is a good deal of pent-up political energy generated by a powerful mix of ethnicity, regionalism and the tradition of chiefdom.

The old colonial rulers carved the continent into nation-states whose peoples and ethnic groups had not been previously united by language, culture or sense of common destiny. With the colonial withdrawal, in some of these countries the centrifugal forces of tribalism that predated foreign rule reasserted themselves.

In order to bridge such differences, leaders often sought to echo earlier chiefly traditions by blurring the distinction between the president as a person and the president as symbol of national unity.

But critics are saying that decades of strong, centralized power, which may have been deemed necessary to demonstrate at least the appearance of national unity, have fostered corruption, mismanagement and economic collapse.

They explain the yearning for democratic procedures now sweeping through Africa as an effort to reverse old practices.